Marshall County High School in the city of Benton was on lockdown whereas the suspect was brought in custody as emergency services tended to the injured, according to officials.
A suspect in the shooting has been detained, Bevin wrote in a Twitter post, saying the details of the incident are under investigation.
The internet users have uploaded photos and videos from the scene.
The Kentucky shooting comes a day after a 15-year-old girl was injured at Italy High School in Texas after a 16-year-old opened fire in the cafeteria. No information on the suspect's motives was provided.